The present invention relates to a scroll-type fluid machine which is constructed by combining an orbiting scroll and a fixed scroll.
Air conditioning units have recently used a scroll-type compressor (scroll-type fluid machine) because of its advantage of efficient compression.
The scroll-type compressor, as shown in FIGS. 4 and 5, is constructed so as to have a scroll-type compressor section h which combines a fixed scroll d including a spiral wrap b disposed on an end plate a and a peripheral wall c surrounding the wrap b with an orbiting scroll g including a spiral wrap f disposed on an end plate e.
Specifically, the compressor section h combines the scrolls d and g so that their wraps b,f engage with each other at a predetermined shifted angle to define a plurality of enclosed spaces i for providing compression process between these wraps.
The volume of the enclosed space i decreases gradually from the peripheral side to the center by revolving the orbiting scroll g around the axis of the fixed scroll d using, for example, a rotary shaft k having an eccentric pin j at its tip. That is to say, the compressor section h compresses a gas by taking advantage of the change in its volume. The orbiting scroll g is provided with a rotation checking mechanism, such as an Oldham's ring, for checking the rotation of the orbiting scroll g, though not shown in the figure.
With some of scroll-type compressors of this type, to prevent gas leakage from the enclosed space i, the fixed scroll d is supported in such a manner as to be displaced in the axial direction, and back pressure chambers m,m having a different pressure are disposed on the back surface side of the fixed scroll d as shown in FIG. 4, so that the fixed scroll d is pressed against the orbiting scroll g in the axial direction.
Such a scroll-type compressor conventionally has a construction described below.
On the back surface side of the fixed scroll d, a discharge cover n is installed to define back pressure chambers m,m between the discharge cover n and the end plate a.
On the back surface of the end plate a of the fixed scroll d, large and small flanges o and p protrude concentrically, whereas on the inner surface of the discharge cover n, concentric flanges q and q protrude so as to engage with the flanges o and p. The engagement of the flanges o and p with the flanges q and q concentrically partitions the back pressure chambers m,m between the end plate a and the discharge cover n. Thus, the back pressure chambers m,m are divided into chambers with a different pressure: for example, a high-pressure chamber r is provided at the center, and an intermediate-pressure chamber is provided around the high-pressure chamber r.
Between the flanges for partitioning the back pressure chambers into the high-pressure chamber side and the low-pressure side, seal members t are interposed to seal the flanges. The fixed scroll d is pressed against the orbiting scroll g by using a discharge pressure and a pressure under compression introduced into the high-pressure chamber r and the intermediate-pressure chamber s.
The seal members t, t used for sealing the back pressure chambers m, m consist of U seals, which are suitable for moving parts, not O-rings, because the fixed scroll d can be displaced.
For the scroll-type compressor, consideration has been given to making the fixed scroll d and the orbiting scroll g of aluminum with the discharge cover being made of ferrous material in order to ensure low cost and light weight.
If the fixed scroll d is made of aluminum, the seal between the high-pressure chamber r and the intermediate-pressure chamber s must overcome a problem of difficulty in sealing because aluminum is a soft material, as well as problems of high temperature and large pressure difference.
Specifically, since the fixed scroll d is displaced relative to the orbiting scroll g side by the back pressure, the aluminum portion in contact with the U seal is easily worn due to the displacement of the fixed scroll d.
For this reason, the technique in which a U seal is merely interposed between the flanges cannot be applied to the scroll-type compressor.
Therefore, a seal construction suitable for the compressor section h having the fixed scroll d made of aluminum has been recommended strongly.